1. Field of the Invention:
This invention relates to cameras whose focal lengths are changeable by changing optical systems, and more particularly to such a camera in which the changing of its optical system is controlled by an electric motor.
2. Description of the Prior Art:
Cameras capable of changing between two or more focal lengths by changing the photographic optical systems are known. Such a so-called focal length changeable camera is disclosed, for example, in U.S. Pat. No. 3,388,650. However, in most of these cameras, changing of the optical system is carried out manually. Motor driven focal length changeable cameras are also known, as disclosed, for example, in Japanese Laid-Open patent application No. SHO 57-146231. However, in such motor driven cameras, focusing of an object to be photographed is carried out either manually or by using another drive source. Prior art variable focal length autofocus cameras have drawbacks in that the focal length of the optical system cannot be changed smoothly. Moreover, the structure of the changing over mechanism and the structure of the focusing mechanism are complicated.